Conductor suspension assembly



1967 H. D. SHORT 3,300,575

CONDUCTOR SUSPENSION ASSEMBLY Filed Oct. 25, 1965 INVENTOR. H. D. SH ORTfmww hza ATTORN EYS United States Patent 3,300,575 CONDUCTOR SUSPENSIONASSEMBLY Herbert Douglass Short, Newmarket, Ontario, Canada,

assignor to Lacal Industries Limited, Newmarket, Ontario, Canada FiledOct. 23, 1965, Ser. No. 503,764 3 Claims. (Cl. 174-144) This inventionrelates to a high voltage electricity con ductor suspension assembly.

In the transmission of electrical energy it is common to transmit eachphase by groups of spaced apart conductors. The phases or groups arespaced apart and are often at potential differences in the order of over400 kv. The conductor groups are supported by conductor suspensionassemblies at towers at spaced apart points along the line. Thisinvention relates to such a conductor assembly and has as its principalobject the reduction of corona losses in transmission by the provisionof an assembly that has a higher corona inception voltage. Corona effectis usually most pronounced at the towers.

Corona losses in the high voltage transmission of electrical energy canbe very substantial and tend to limit the voltage that a line can beoperated at under many conditions. .Corona may be described as amanifestation of ionization formed in air at breakdown of the air due tohigh potentials. It represents a loss of electrical power from thetransmission line and must be kept within tolerable limits. At the sametime it is desired to transmit as much power as possible over a givenline.

It will be apparent that any device that has the effect of raising theionization ignition or corona inception voltage of a line will increasethe line efliciency because it will raise the operating voltage for agiven tolerable corona loss.

It is well known that corona is most apparent at sharp edges in a pieceof conducting equipment and designers usually try to eliminate sharpedges where corona is a factor to be designed for. This inventioneliminates the effect of sharp edges in a suspension clamp by the uniqueexpedient of providing a spheroidal shielding link to connect eachconductor clamp of the assembly to the suspension plate, such spheroidsbeing of sufiicient dimensions to function as electrostatic shieldsthereby reducing the intensity or concentration of the electric fieldand at the same time increasing the electrostatic capacity of theinsulators immediately adjacent to the suspension assembly which in turnreduces the voltage distribution across the insulators and hence theirsusceptibility to corona formation.

Generally speaking, a conductor suspension assembly according to thisinvention comprises a suspension plate, a plurality of conductor clampseach having jaws with a jaw axis adapted to align with the axis of aconductor in use and a spherical link menrber connecting each of saidconductor clamps to said suspension plate with its jaw axissubstantially parallel to the jaw axis of the other of said plurality ofconductor clamps. The invention will be clearly understood afterreference to the following detailed specification read in conjunctionwith the drawings.

In the drawings:

FIGURE 1 is an illustration of a conductor suspension assembly accordingto the invention with one clamp and its link in exploded form and withone link broken away;

FIGURE 2 shows a portion of a clamp, and

FIGURE 3 illustrates the connection of a link to an arm of the plate.

The conductor suspension assembly shown comprises a suspension plateadapted for suspension from a transmission tower in the usual way andpreferably made from aluminum according to standard practice. There arefour metal similar conductor clamps carried by plate 10', each "icecomprising cooperating jaws 12 and 14 operable into and out of clampingarrangement with respect to each other by bolts 16 and nuts 18. In usecable is gripped in the longitudinally extending cylindrical cavity 20,the axis of which is herein defined as the jaw axis.

It will be noted that the cross-section of the conductor clamps is ovalin shape and that the jaw axis, which coin ides in use with thelongitudinal axis of a cable gripped within the jaw, is located towardsthe outer end of the jaw cross-section. These clamps have been designedwith a view to having the cross-section thereof conform to anequipotential surf-ace of the electrostatic field created by fourcurrent carrying conductors mounted in the assembly. The shaping of thecross-section of the clamps with a view to having their outer surfacecorrespond to the equipotential surface of the electrostatic fieldcreated has been described and claimed in my copending United Statesapplication Serial No. 376,186, filed June 18, 1964.

A metal spheroidal shielding link 22, in this case essentiallyspherical, connects each of the clamps to the plate 10. In theembodiment illustrated the shielding link 22 is cast integral with thejaw section 12. It has a socket [formed in its free end and is joined tothe plate 10 by means of a bolt 24 that extends through one side of thesphere, through a hole 26 in an arm of plate 10 and into a threaded bore25 in the other side of sphere 22. Bolt 24 preferably has a lock washerunder its head.

The socket into which arm 26 extends is formed to per mit a certainamount of pivotal movement between the parts, as will be apparent fromFIGURE 3, to permit variation of the angle of inclination of theconductors carired thereby at the towers in use.

In use four conducting cables, constituting a bundle, are retained bythe four clamps of the assembly which is suspended from a transmissiontower of a power transmission system. The four cables each commonlycarry current of one of three phases in a three phase system andadjacent and similar assemblies carry similar conducting cables of theother phases.

It is well understood that under such conditions loss due to coronaincreases with the intensity of the electrostatic field at the surfaceof conducting bodies. Thus, if the bodies have sharp points, theintensity of the electric field at those points is most likely to bequite high and corona will manifest itself at those points, as thetransmitting potential increases. By increasing the surface area of suchpoints by rounding the body the intensity of the electric field at thesurface is reduced and the voltage at which corona effect becomesapparent is raised.

This invention employs a spheroidal connecting device for connecting theclamp to the plate and is thought to be the ultimate type of connectionfor connecting the clamp to the plate from the point of view of reducingcorona loss. The diameter of the spheroidal link 22 must be large enoughto result in a surface area that reduces the intensity of theelectrostatic field at the surface of the sphere to a point where noobjectionable corona effect exists when each of the assembly clamps hasa conductor clamped therein and the desired operating transmissionvoltage exists. It will be apparent that as the transmitting volt-ageincreases that the size of the sphere 22 will have to be increased inorder to reduce the electrostatic intensity at the surface of the sphereto a value that will eliminate or reduce corona losses to the desiredlevel. Thus, the surface area of the sphere 22 shields the sharp pointsof the connection of the clamp to the plate that would otherwise existif the sphere were not incorporated. For example, the bolt 24 the headof which is embedded in one side of the sphere 22 would if unshielded bythe sphere 22 present a rather sharp corner at which the electrostaticfield surrounding the conducting cables in use would tend to beintensified. Corona would tend to form at this and other sharp points atthe connection first. However, by providing the shielding sphere theelectric field intensity is reduced at this point for *a given voltageand it is a matter of choice to select the size of the sphere that willreduce the intensity to a point that will eliminate corona at this pointin any given design.

A sphere 22, having a diameter of about 3% inches, has provedsatisfactory in eliminating corona effect in tests where a bundle ofconductors carried in the assembly as illustrated at spacings of about19 inches from each other in the horizontal and vertical direction wasoperated at a voltage of 310 kilovolts to ground at a distance of 10feetto ground.

The shape of link connector 22 has been illustrated as spherical butitis not intended that the invention be so limited. A link of a shapeapproaching the shape of a sphere i.e. spheroidal would fulfill thepurpose of an eflective shield for the sharp edges. Thus an ellipsoidalor similar solid of revolution of a curve is contemplated. The essenceof the invention is a link having a rounded but not necessarily roundoutline that will result in a surface area to reduce electrostatic fieldintensity and act as an efficient corona shield.

What I claim as my invention is:

1. A high voltage conductor suspension assembly for a bundle ofconductors of a single phase comprising a suspension plate, a pluralityt conductor clamps, each having jaws with a jaw axis adapted to alignwith the axis of a conductor in use, and a spheroidal corona shieldinglink members between each clamp and said conductor plate having aspheroidal interconnecting part electrically connecting each of saidconductor clamps to said suspension plate with the jaw axis of each ofsaid conductor clamps substantially parallel to the jaw axis of each ofthe other of said plurality of conduct-or clamps.

2. A high voltage conductor suspension assembly as claimed in claim 1,in which said spheroidal member is formed from a common piece ofmaterial with said respective clamp.

3. A high voltage conductor assembly as claimed in claim 1 in which saidspheroidal member is spherical.

References Cited by the Examiner UNITED STATES PATENTS 2,806,897 9/ 1957Sheadel et al 174144 X FOREIGN PATENTS 65 3,027 11/1962 Canada. 685,5031/1953 Great Britain. 63,677 2/ 1913 Switzerland.

OTHER REFERENCES Ohio Brass Advertisement, Electrical World, vol. 143,

No. 11, March 14, 1955, page 11.

LARAMIE E. ASKIN, Primary Examiner.

1. A HIGH VOLTAGE CONDUCTOR SUSPENSION ASSEMBLY FOR A BUNDLE OFCONDUCTORS OF A SINGLE PHASE COMPRISING A SUSPENSION PLATE, A PLURALITYOF CONDUCTOR CLAMPS, EACH HAVING JAWS WITH A JAW AXIS ADAPTED TO ALIGNWITH THE AXIS OF A CONDUCTOR IN USE, AND A SPHEROIDAL CORONA SHIELDINGLINK MEMBERS BETWEEN EACH CLAMP AND SAID CONDUCTOR PLATE HAVING ASPHEROIDAL INTERCONNECTING PART ELECTRICALLY CONNECTING EACH OF SAIDCONDUCTOR CLAMPS TO SAID SUSPENSION PLATE WITH THE JAW AXIS OF EACH OFSAID CONDUCTOR CLAMPS SUBSTANTIALLY PARALLEL TO THE JAW AXIS OF EACH OFTHE OTHER OF SAID PLURALITY OF CONDUCTOR CLAMPS.